KR100778199B1 - Ultraviolet-curable pressure sensitive adhesive composition and ultraviolet-curable pressure sensitive adhesive sheet - Google Patents

Abstract

An ultraviolet-curable pressure-sensitive adhesive composition comprising an ultraviolet-curable pressure-sensitive adhesive component and a phosphorus photopolymerization initiator is disclosed. Moreover, the ultraviolet-curable adhesive sheet obtained by apply | coating the said ultraviolet-curable adhesive composition on a base material is disclosed. The ultraviolet-curable adhesive composition may maintain ultraviolet curability even when the ultraviolet-curable pressure sensitive adhesive sheet is in contact with the washing water for a long time.

UV-curable pressure-sensitive adhesive composition, ultraviolet-curable pressure-sensitive adhesive sheet

Description

Ultraviolet-curable pressure sensitive adhesive composition and ultraviolet-curable pressure sensitive adhesive sheet

The present invention relates to an ultraviolet-curable pressure-sensitive adhesive composition and an ultraviolet-curable pressure-sensitive adhesive sheet obtained by applying the pressure-sensitive adhesive composition on a substrate. More specifically, the present invention relates to a pressure sensitive adhesive sheet used for the processing of precision parts such as semiconductor wafers.

Semiconductor wafers, such as silicon wafers and gallium arsenide wafers, are manufactured to have large diameters, which are cut (diced) into small pieces and then enter a subsequent mounting process. In this case, dicing, cleaning, drying, expanding, pick-up, and mounting processes are successively performed on the semiconductor wafer previously adhered to the adhesive sheet (dicing sheet).

To remove cutting dust and cutting heat, the wafer is diced with high pressure spraying.                         

The dicing sheet used for the above purpose requires an adhesive strength such that the wafer (chip) does not peel off during the dicing operation, while the weak adhesive force that the chip can easily peel off during the picking operation. It is also necessary. Moreover, it is required to leave no tack residue on the back side of the chip and not to contaminate the chip.

For the same reason as above, an adhesive sheet having an ultraviolet-curable pressure sensitive adhesive layer capable of reducing or losing adhesive force is used as a dicing sheet. The ultraviolet-curable pressure sensitive adhesive includes an ultraviolet-curable pressure sensitive adhesive component and a photopolymerization initiator as main components.

In the field of electronic technology, there has always been a demand for miniaturization of chips. As chips become smaller, the time required for dicing the wafer also becomes longer. That is, in order to manufacture a plurality of small chips from the same size wafer, the spacing between dicing lines is narrowed, the number of dicing lines is increased, and the time required for dicing is longer. As a result, the dicing sheet comes into contact with the washing water for a long time.

As described above, when the dicing time is long, even if the dicing sheet is irradiated with ultraviolet rays during the pick-up process after dicing, the adhesive force of the ultraviolet-curable pressure-sensitive adhesive layer is not sufficiently lowered, thus making it difficult to pick up chips.

The present invention has been made in view of the above-described prior art, and the ultraviolet-curable pressure-sensitive adhesive composition and the pressure-sensitive adhesive composition which can maintain ultraviolet curability even when the dicing sheet using the adhesive composition of the present invention is in contact with the washing water for a long time. It is an object to provide an ultraviolet-curable pressure-sensitive adhesive sheet obtained by coating on a substrate.

The ultraviolet-curable pressure sensitive adhesive composition according to the present invention includes an ultraviolet-curable pressure sensitive adhesive component and a phosphorous type photopolymerization initiator.

In the present invention, the phosphorus photopolymerization initiator is preferably an acylphosphine oxide compound, more preferably a compound having a CO-P0 bond in the molecule, and particularly preferably a compound represented by the following formula:

In formula, R <^1> is the aromatic group which may have a substituent, and R <^2> and R <^3> is either any of the phenyl group, the alkyl group, the alkoxy group, and the aromatic acyl group which may each independently have a substituent.

In the ultraviolet-curable pressure-sensitive adhesive composition of the present invention, the phosphorus photopolymerization initiator is preferably contained in an amount of 0.005 to 20 parts by weight based on 100 parts by weight of the ultraviolet-curable pressure-sensitive adhesive component.

The ultraviolet-curable pressure sensitive adhesive sheet according to the present invention is obtained by applying the ultraviolet-curable pressure sensitive adhesive composition on a substrate.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail. The ultraviolet-curable pressure sensitive adhesive composition according to the present invention includes an ultraviolet-curable pressure sensitive adhesive component and a phosphorus photopolymerization initiator.

As the ultraviolet-curable pressure-sensitive adhesive component, any of various ultraviolet-curable pressure-sensitive adhesive components known to date can be used without limitation, but in general, a component containing an acrylic pressure-sensitive adhesive and an ultraviolet polymerizable compound as a main component is used.

UV-polymerizable compounds used in the ultraviolet-curable pressure-sensitive adhesive component, for example, three-dimensional network by light irradiation, as disclosed in Japanese Patent Publication Nos. 196956/1985 and 223139/1985 Low-molecular-weight compounds having at least two or more intramolecular photopolymerizable carbon-carbon double bonds capable of forming are widely used. Examples of such compounds are trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, di Pentaerythritol hexaacrylate, 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, polyethylene glycol diacrylate and commercially available oligoester acrylates.

In addition to the above-mentioned acrylate compounds, urethane acrylate oligomers may also be used as the ultraviolet polymerizable compound. Urethane acrylate oligomers include polyester or polyether type polyol compounds and polyisocyanate compounds (eg, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylene diisocyanate, 1 Terminal-isocyanate urethane prepolymers obtained by reacting 4-4-xylene diisocyanate, diphenylmethane-4,4-diisocyanate) are acrylates or methacrylates having hydroxyl groups (e.g., 2-hydroxyethyl Acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, polyethylene glycol acrylate and polyethylene glycol methacrylate).

Among the ultraviolet-curable pressure sensitive adhesive components, the blending ratio of the acrylic pressure sensitive adhesive and the ultraviolet polymerizable compound is as follows. It is preferable that an ultraviolet polymerizable compound is used in the quantity of 50-200 weight part with respect to 100 weight part of acrylic adhesives. In this case, the resultant adhesive sheet has a large initial adhesive force, and the adhesive force greatly decreases after ultraviolet irradiation. Therefore, separation of the adherend and the acrylic ultraviolet-curable pressure-sensitive adhesive layer becomes easy, and the adherend can be picked up.

In addition, the ultraviolet-curable pressure sensitive adhesive component may include an ultraviolet-curable copolymer having an ultraviolet polymerizable group in the side chain. Such ultraviolet-curable copolymers have both sticky and ultraviolet curable properties. Ultraviolet-curable copolymers having an ultraviolet polymerizable group in the side chain are described in detail in, for example, Japanese Patent Publication Nos. 32946/1993 and 27239/1996.                     

The acrylic ultraviolet-curable pressure sensitive adhesive has sufficient adhesive strength to the adherend before ultraviolet irradiation, but after ultraviolet irradiation, the adhesive strength is significantly reduced. That is, although the said adherend can be hold | maintained with sufficient adhesive force before ultraviolet irradiation, an adherend can be easily peeled off after ultraviolet irradiation.

The ultraviolet-curable pressure-sensitive adhesive composition according to the present invention includes a known ultraviolet-curable pressure-sensitive adhesive component and phosphorus-based photopolymerization initiator as mentioned above.

Phosphorus-based photopolymerization initiator is a compound containing phosphorus in the molecule, when the compound is exposed to ultraviolet rays, radicals having a polymerization initiation capacity are formed. As said phosphorus photoinitiator, an acyl phosphine oxide compound is preferable, and the compound which has a CO-P0 bond in a molecule | numerator is more preferable. As said phosphorus photoinitiator, it is especially preferable to use the compound represented by a following formula.

  Formula (1)

In said formula, R <^1> is the aromatic group which may have a substituent, Preferably they are dimethylphenyl, trimethylphenyl, trimethoxyphenyl, dimethoxyphenyl, phenyl, etc.

R <^2> and R <^3> is respectively independently any of a phenyl group, an alkyl group, an alkoxy group, and an aromatic acyl group which may have a substituent.

As a phenyl group which may have a substituent, dimethylphenyl, trimethylphenyl, trimethoxyphenyl, dimethoxyphenyl, phenyl, etc. are preferable, Especially preferably, it is a phenyl group.

As the alkyl group which may have a substituent, 2-methylpropyl, 2,4,4-trimethylpentyl and the like are preferable, and a 2,4,4-trimethylpentyl group is particularly preferable.

As an alkoxy group which may have a substituent, an ethoxy group is especially preferable.

As an aromatic acyl group which may have a substituent, R <^1> -CO- group (R <^1> is the same as the above) is preferable.

Thus, examples of particularly preferred phosphorus photopolymerization initiators used in the present invention include the following compounds.

Bis (2,4,6-trimethylbenzoyl) phenylphosphineoxide

2,4,6-trimethylbenzoyldiphenylphosphine oxide

Bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphineoxide

The phosphorus-based photopolymerization initiators mentioned above may be used alone or in combination of two or more thereof, or may be used in combination with other known photopolymerization initiators.

Examples of photopolymerization initiators that can be used in combination include photopolymerization initiators such as benzoin compounds, acetophenone compounds, titanocene compounds, thioxanthone compounds and peroxide compounds; And photosensitizers such as amines and quinones. Specifically, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,2-dimethoxy-1,2-diphenylethane-l-one, Benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyldiphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β-chloroanthra Quinone etc. are mentioned.

In the ultraviolet-curable pressure-sensitive adhesive composition of the present invention, the phosphorus photopolymerization initiator is preferably 0.005 to 20 parts by weight, more preferably 0.01 to 10 parts by weight, particularly preferably 0.05 to about 100 parts by weight of the ultraviolet-curable pressure sensitive adhesive component. It is contained in 1 weight part.

When used in combination with other photopolymerization initiators, the total amount of the photopolymerization initiators is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, particularly preferably 100 parts by weight of the ultraviolet-curable pressure sensitive adhesive component. It is included in 3 parts by weight or less.

The phosphorus photopolymerization initiator can maintain the ultraviolet curability of the ultraviolet-curable pressure-sensitive adhesive component even if it is in contact with the washing water for a long time.

The above-mentioned ultraviolet-curable pressure-sensitive adhesive composition has sufficient adhesive strength to the adherend before ultraviolet irradiation, but after the ultraviolet irradiation, the adhesive strength is significantly lowered. That is, before the ultraviolet irradiation, the adhesive sheet and the adherend can be combined with sufficient adhesive force to maintain the adherend on the adhesive sheet, but after the ultraviolet irradiation, the adhesive sheet can be easily peeled from the cut adherend.

In order to increase the modulus of elasticity of the ultraviolet-curable pressure-sensitive adhesive composition and to impart greater cohesive force to the composition, a crosslinking agent may be added. The crosslinking agent provides three-dimensional crosslinking of the ultraviolet-curable pressure-sensitive adhesive composition to impart sufficient elastic modulus and cohesive force to the composition. As the crosslinking agent, known compounds such as polyisocyanate compounds, polyepoxy compounds, polyaziridine compounds or chelate compounds can be used. Examples of polyisocyanate compounds include toluylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and addition products of these polyisocyanates with polyhydric alcohols. Examples of polyepoxy compounds include ethylene glycol diglycidyl ether and diglycidyl terephthalate acrylate. Examples of polyaziridine compounds include tris 2,4,6- (1-aziridinyl) -l, 3,5-triazine and tris (1- (2-methyl) aziridinyl) triphosphatazine It includes. Examples of chelate compounds include ethyl acetoacetate aluminum diisopropylate and aluminum tris (ethylacetoacetate). These compounds may be used alone or as mixtures thereof.

The crosslinking agent is preferably added in an amount of 0.005 to 20 parts by weight, more preferably 0.01 to 10 parts by weight based on 100 parts by weight of the ultraviolet-curable pressure-sensitive adhesive composition.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention is prepared by appropriately mixing the above components with other components optionally added.

The ultraviolet-curable pressure sensitive adhesive sheet according to the present invention is obtained by applying the ultraviolet-curable pressure sensitive adhesive composition on a substrate.

There is no particular limitation on the substrate, and various thin sheets such as paper, metal foil, and synthetic film can be used. Among them, it is preferable to use a synthetic resin film in terms of water resistance and heat resistance. Examples of the synthetic resin films include polyolefin films such as polyethylene film, polypropylene film, polybutene film and polymethylpentene film; And, polyvinyl chloride film, polyvinylidene chloride film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polybutadiene film, polyurethane film, ethylene / vinyl acetate copolymer film, ethylene / (meta ) Acrylic acid copolymer films, ethylene / (meth) acrylate copolymer films, ionomer films, polystyrene films, and other films such as polyamide films.

The thickness of the said base material is 5-300 micrometers normally, Preferably it is 10-20 micrometers. The substrate may be a single-layered product of any one of the various films, or may be a laminated product of the various films.

In order to improve the adhesiveness between the substrate and the pressure-sensitive adhesive layer, it is possible to perform a corona treatment on the upper surface of the substrate, that is, the surface on which the ultraviolet-curable pressure-sensitive adhesive layer is installed, or to coat another layer such as primer coating.

UV-curable pressure-sensitive adhesive sheet of the present invention, a generally known method such as a roll coater (knife coater), knife coater (grave coater), gravure coater (dieure coater), reverse coater (reverse coater) It can be prepared by applying the ultraviolet-curable pressure-sensitive adhesive composition to a suitable thickness using them, and then drying the applied layer. The thickness of the adhesive layer formed from an ultraviolet-curable adhesive composition is 1-100 micrometers normally, Preferably it is 5-50 micrometers. After production, in order to protect the pressure-sensitive adhesive layer, a release sheet may be attached to the ultraviolet-curable pressure-sensitive adhesive layer.

Next, a brief description will be given of a method of applying the ultraviolet-curable pressure sensitive adhesive sheet of the present invention to the processing of a semiconductor wafer.

When the peelable sheet is provided on the upper surface of the pressure sensitive adhesive sheet, the peelable sheet is removed first, and then the pressure sensitive adhesive sheet is installed so that the pressure sensitive adhesive layer faces upward, and the semiconductor wafer to be diced is attached to the upper surface of the pressure sensitive adhesive layer. Next, the wafer is continuously diced, cleaned and dried in this state. In these steps, the wafer chips are sufficiently adhered and held on the pressure sensitive adhesive sheet so that the wafer chips do not fall off from the pressure sensitive adhesive sheet during these processes.

Then, each wafer chip is picked up from the adhesive sheet and mounted on a predetermined substrate. Before or during the pick-up process, ultraviolet rays are irradiated onto the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet to polymerize the ultraviolet-polymerizable component contained in the ultraviolet-curable pressure-sensitive adhesive layer. When the ultraviolet-ray polymerizable component is polymerized by irradiating the pressure-sensitive adhesive layer, the pressure-sensitive adhesive force of the pressure-sensitive adhesive is greatly reduced, and only a slight adhesive force remains.

It is preferable to perform ultraviolet irradiation to an adhesive sheet from the base material side in which an adhesive layer is not provided. In this case, the base material is required to have light transmittance.

Next, when it is necessary to increase the distance between the chips, the adhesive sheet is expanded. Subsequently, the chips are picked up using a pickup device such as a suction collet, and then mounted on a predetermined substrate.

The present invention is illustrated by the following examples, but the present invention is not limited to these examples.

In addition, in the following Examples and Comparative Examples, "adhesive force before ultraviolet irradiation", "adhesive force after ultraviolet irradiation (not exposed to clean water)" and "adhesive force after ultraviolet irradiation (exposed to clean water)" are the following methods Evaluated.

Adhesion before UV irradiation

Using the respective adhesive sheets obtained in Examples or Comparative Examples, 180 ° peeling force (mN / 25mm) was measured under the following conditions, and the measured peeling force was taken as the adhesive force before ultraviolet irradiation.

180 ° peeling force measurement conditions

In an atmosphere of 23 ° C. and 65% RH, a 2 kg rubber roller was reciprocated on the pressure sensitive adhesive sheet placed on the Si wafer polishing surface (Ra = 0.16 to 0.2 μm) to superimpose the pressure sensitive adhesive sheet on the Si wafer. After standing for 20 minutes, the peel force of the pressure sensitive adhesive sheet was measured in accordance with JIS-Z0237 at a peel rate of 30 mm / min using a universal tensile tester (trade name: TENSILON / UTM-4-100, manufactured by Orientech Co., Ltd.). .

Adhesion after UV irradiation (not exposed to washing water)

Adwill RAD200O m / 8 (trade name, manufactured by Lintec, Inc., illuminance: 220 mW / cm 2, quantity of light: 160 mJ / cm 2, nitrogen flow rate 35) in a state where the adhesive layer was exposed to each of the pressure sensitive adhesive sheets obtained in Examples or Comparative Examples. (l / min) was used to irradiate ultraviolet rays from the substrate side.

Using the adhesive sheet treated above, 180 ° peeling force (mN / 25) was measured under the same conditions as described above, and the measured peeling force was determined as the adhesive force (not exposed to clean water) after ultraviolet irradiation.

Adhesion after UV irradiation (exposed to clean water)

Each pressure-sensitive adhesive sheet obtained in Examples and Comparative Examples was exposed to washing water under the following conditions, and within 10 minutes after exposure to washing water, Adwill RAD2000 m / 8 (trade name, manufactured by Lintec Corporation, roughness: 220 mW / cm 2, light) Amount: 160 mJ / cm 2, nitrogen flow rate 35 L / min) to irradiate ultraviolet rays from the substrate side.

Using the pressure-sensitive adhesive sheet treated above, l80 ° peeling force (mN / 25mm) was measured under the same conditions as described above, and the measured peeling force was determined as the adhesive force after exposure to ultraviolet light (exposed to clean water).

Washing water exposure condition

The pressure-sensitive adhesive sheet is adhered to the ring frame, and the surface of the pressure-sensitive adhesive layer is exposed to washing water for 60 minutes at a speed of 3 L / min with Dicer (A-WD-4000B, manufactured by Tokyo Precision Co., Ltd.), followed by spin drying. (1500 rpm, 180 seconds).

The following were used as an ultraviolet-curable adhesive component, a photoinitiator, and other components.

UV-curable adhesive component A

Obtained by reaction of 100 weight part of copolymers (weight-average molecular weight: 650,000) which have 85 weight part of n-butyl acrylate and 15 weight part of 2-hydroxyethyl acrylate with 16 weight part of methacryloyloxyethyl isocyanate UV-curable pressure sensitive adhesive component.

The polymerizable double bond content per 100 g of the ultraviolet-curable pressure sensitive adhesive component was 0.14 mol.

Photoinitiator B

Bl: bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide

B2: 2,4,6-trimethylbenzoyldiphenylphosphine oxide

B3: bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide

B4: 2,2-dimethoxy-1,2-diphenylethan-1-one

B5: 1-hydroxycyclohexyl phenyl ketone

Crosslinker C

Adducts of Toluylene Diisocyanate and Trimethylolpropane

Example 1

Each component of Table 1 was mixed in the ratio of Table 1, and the ultraviolet-curable adhesive composition was obtained. The pressure-sensitive adhesive composition was applied on a release film (exfoliated on polyethylene terephthalate film, thickness: 38 μm), and then transferred to a base material (ethylene-methacrylic acid copolymer film, thickness: 80 μm), and the thickness was 10 μm. The pressure-sensitive adhesive sheet for wafer adhesion having the ultraviolet-curable pressure-sensitive adhesive layer was prepared.

The results are shown in Table 1.

Examples 2-3 and Comparative Examples 1-2

Each component of Table 1 was mixed in the ratio of Table 1, and the ultraviolet-curable adhesive composition was obtained. Except using this adhesive composition, operation similar to Example 1 was performed.

The results are shown in Table 1.

Table 1-a Adhesive force (mN / 25㎜) Before UV irradiation After ultraviolet irradiation Not exposed to cleaning water Exposed to cleaning water Example 1 5490 280 270 Example 2 5640 130 210 Example 3 5930 140 280 Comparative Example 1 6190 150 1650 Comparative Example 2 5880 270 700

Table 1-b

UV-curable pressure-sensitive adhesive composition (parts by weight) UV-curable pressure sensitive adhesive component A Photoinitiator B Crosslinker C B1 B2 B3 B4 B5 Example 1 100 0.16 0.062 Example 2 100 0.6 0.062 Example 3 100 1.65 1.65 0.062 Comparative Example 1 100 6 0.062 Comparative Example 2 100 3.27 2.7 0.062

The adhesive force of the adhesive sheet obtained by the comparative example did not fall enough even after ultraviolet irradiation. On the other hand, the adhesive force of the pressure-sensitive adhesive sheet obtained in the example was sufficiently lowered after the ultraviolet irradiation in both the exposed and unexposed wash water.

According to the present invention, even when the adhesive sheet is in contact with the washing water for a long time during the dicing process, the ultraviolet curability of the ultraviolet-curable pressure sensitive adhesive component is maintained, and the chip can be picked up without difficulty.

Claims (6)

An ultraviolet-curable pressure-sensitive adhesive composition comprising an ultraviolet-curable pressure-sensitive adhesive component and a phosphorus photopolymerization initiator, The ultraviolet-curable pressure-sensitive adhesive component, (i) an ultraviolet-curable copolymer having an ultraviolet polymerizable group in the side chain, or (ii) 100 to 200 parts by weight of an acrylic adhesive and 50 to 200 parts by weight of an ultraviolet polymerizable compound selected from an acrylate compound and a urethane acrylate oligomer having two or more photopolymerizable carbon-carbon double bonds; The phosphorus-based photopolymerization initiator is contained in 0.005 to 20 parts by weight based on 100 parts by weight of the ultraviolet-curable pressure-sensitive adhesive component, UV curable pressure-sensitive adhesive composition. The ultraviolet-curable pressure-sensitive adhesive composition of claim 1, wherein the phosphorus photopolymerization initiator is an acylphosphine oxide compound. The ultraviolet-curable pressure-sensitive adhesive composition of claim 2, wherein the acylphosphine oxide compound is a compound having a CO-PO bond in a molecule. The ultraviolet-curable pressure-sensitive adhesive composition of claim 3, wherein the acylphosphine oxide compound is a compound represented by the following formula:

In formula, R <^1> is the aromatic group which may have a substituent, R <^2> and R <^3> is respectively independently any of the phenyl group, the alkyl group, the alkoxy group, and the aromatic acyl group which may have a substituent. delete The ultraviolet-curable adhesive sheet obtained by apply | coating the ultraviolet-curable adhesive composition of Claim 1 on a base material.